"I wanted very much to have Cobie in the pilot because as much as anyone else, she is S.H.I.E.L.D.," series co-creator Joss Whedon said in a statement to The Hollywood Reporter. "She's cool and commanding, and has the dry humor that plays so well with Clark's. Also, if she's in it I get to hang out with Cobie."

Smulders, who had a role in "The Avengers 2" and will appear in "Captain America: The Winter Soldier," revealed in late January that there had been "definite talks" for her to appear in the ABC series, but the production schedule of "How I Met Your Mother" was proving an obstacle. Whedon later said the actresses' commitments "will permit very little" involvement, "but if we can get a hold of her any time, we will."

And clearly they did. However, Smulders' appearance on "Agents of S.H.I.E.L.D." may not be merely a one-time deal. According to Entertainment Weekly, she's expected to appear "occasionally" on the show. But with "HIMYM" entering its final season, her schedule could free up for Season 2 "Agents of S.H.I.E.L.D."